Numerical analysis of pre-dryout sequences through the route of interfacial evolution in annular gas-liquid two-phase flow with phase change

Numerical modeling of two-phase annular flow boiling has been carried out inside a tube using volume of fluid based computational multifluid dynamics. The proposed numerical methodology has been validated with available experimental results from literature. The stages of bubble nucleation, growth, merging, bursting, droplet entrainment, film rewetting, and dryout has been clearly visualized for diabatic annular mist flow. Plots of liquid phase fraction and average heat transfer coefficient were plotted which shows decreasing trends with axial space. Effect of different degrees of superheats and gas-liquid velocities at a higher working pressure of 40 bar have been studied, which can be commonly observed in boiling water reactor (BWR) conditions. Dryout is found to happen early in the axial length if the degree of superheat and flow velocities increases. The chaotic interfacial behavior has been analyzed with mean, standard deviation and attractor plot of space time-varying values of liquid phase fraction. (C) 2019 Elsevier Ltd. All rights reserved.